In a minimill process, a strand solidified in a continuous caster is rolled using the high temperature of the strand. Since such minimill processes incurs relatively low equipment costs and operating costs, as compared to conventional processes, minimill processes are now widely used.
In addition to such continuous casting and rolling processes, a discontinuous rolling process may be performed independently of the continuous casting process. This technique is disclosed in Korean Patent Application Laid-open Publication No. 1990-7001437.
That is, as illustrated in FIGS. 1A and 1B, a rolling process may be continuously performed, together with a continuous casting process, or a rolling process may be discontinuously performed together with a continuous casting process in a discontinuous rolling mode.
FIG. 1A illustrates equipment 1′ for a continuous rolling process. Referring to FIG. 1A, a strand 2′ having a constant thickness is produced by a continuous caster 100′, and the strand 2′ is primarily rolled by a first rolling unit 210′. Thereafter, while maintaining the temperature of the strand 2′ using an insulator K, the strand 2′ is transferred to a heater 300′ and heated to a final rolling temperature, and then finally rolled by a second rolling unit 220′ to produce a steel sheet 2a′. After the final rolling, the steel sheet 2a′ is cut by a cutting machine 410′ and wound around a rewinder R. In this manner, a rolled steel sheet 2a′ may be produced.
FIG. 1B illustrates equipment 1′ for a discontinuous rolling process. Referring to FIG. 1B, a strand 2′ having a constant thickness is produced by a continuous caster 100′, and the strand 2′ is primarily rolled by a first rolling unit 210′. Thereafter, the strand 2′ is cut using a cutting machine 410′ before the strand 2′ is transferred to a second rolling unit 220′. Therefore, a rolling process may be performed independently of the rate of casting of the continuous caster 100.
A slab cut from the strand 2′ is wound around an intermediate coiler, and then the slab is transferred to a second rolling unit 220′ after being heated to a rolling temperature by a heater 300′. The second rolling unit 220′ rolls the slab to produce a rolled steel sheet 2a′, and a rewinder R winds the rolled steel sheet 2a′. 
Even when a steel sheet 2a′, wound around the intermediate coiler, is unwound and transferred to the second rolling unit 220′ during switching from the discontinuous rolling process to a continuous rolling process, the continuous caster 100′ continuously produces a steel sheet 2a′. Thus, a portion of the steel sheet 2a′ is inevitably cut and discarded.
To address this problem, research into continuous casting and rolling apparatuses and methods is needed.